Democrats Hillary Clinton and Barack Obama are locked in a tight battle for their party's presidential nomination, a struggle that could go on for weeks or even months. Republican John McCain, meanwhile, is the clear frontrunner for his party's nomination. The process for choosing the party presidential nominees is lengthy, complicated and confusing. VOA National Correspondent Jim Malone has a look at the basics of the process from Washington.

The objective is the same in both parties - win enough delegates to become the party nominee for president at the national conventions later this year.

To do that, candidates compete state by state for delegates who will support them at the national conventions, where the parties make the final decision on who will be their presidential candidates.

To win delegates, the candidates compete in state primaries and caucuses where voters express their preferences. Candidates who win the primaries and caucuses are awarded delegates, though how that is done varies between the two major political parties.

It is the individual states and political parties that decide what kind of delegate selection process they want in a given state.

Stuart Rothenberg publishes a political newsletter in Washington and was a guest on VOA's Talk To America webchat.

"The parties are running these systems, or trying to run these nominating systems as they so choose," he noted. "This is not the United States government adopting a system and imposing it on the parties. And so again, it tends to be chaotic."

That is why New Hampshire and other states favor the use of a party primary, where voters go to their local polling places and vote, while other states like Iowa prefer party caucuses. Caucuses require voters to attend local meetings and express their preferences for president.

Historically, the idea of voters choosing the party presidential nominees is relatively new, beginning in the late 1960s. Before that, state and local elected officials and party bosses around the country effectively controlled the presidential nomination process and chose the party nominees.

The classic description is that for many years, the presidential candidates were chosen in smoke-filled rooms by party bosses and political insiders.

That all began to change in the Democratic Party in the late 1960s and early 1970s when reformers demanded a greater role in the presidential nominating process.

"Beginning in the 1960s, the Democratic Party went through a process of reform, and those reforms moved away from a process that was dominated by insiders and dominated by inside politics to the emergence of a process where voters determined the outcome," said Tad Devine, a longtime Democratic political strategist.

In addition to switching to a system of choosing party nominees by primaries and caucuses, the Democrats also instituted the requirement that delegates would be allocated on a proportional basis.

That means both the winner and loser in close races would get a portion of the delegates at stake.

"To see that there would not only be more open elections, primaries or caucuses, in which the rank and file would have a real voice, but also that the results would not be hinging simply on narrow victories," said Bruce Miroff, who teaches politics at the State University of New York at Albany. "And so proportional representation in the Democratic Party really starts in the 1972 convention rules."

Republicans also select their presidential nominees through a series of primaries and caucuses. But most of the Republican contests are winner-take-all votes in which the winner of a given primary or caucus is awarded all the delegates at stake.

About 20 percent of the Democratic delegates are referred to as superdelegates, convention delegates who are not elected through the primaries and caucuses.

Superdelegates are made up of elected officials like governors, senators, members of Congress or local elected officials, as well as high-ranking party officials.

"Those are positions held open for party leaders and elected officials of that party," explained Stephen Wayne, a professor of government at Georgetown University in Washington. "Unlike the regular delegates who are elected by the people and pledged to support a certain candidate, the superdelegates are unpledged."

Some superdelegates do commit to a candidate in advance. Some do it privately, others announce it publicly.

Republicans have a similar group of what they call unpledged delegates who are not required to indicate a candidate preference before the party convention.

In this year's extremely close Democratic race, the superdelegates could wind up playing a very important role.

Professor Miroff says that was the intention of party leaders when they created the concept of superdelegates in the 1970s.

"For the first time since the system was created, superdelegates play the role they were supposed to play as party leaders who worry about the success of the party, rather than individuals committed to particular ideology or a particular candidate," he said.

Clinton and Obama are very close in the delegate count. Most news organizations estimate each candidate has between 800 and 900 delegates. A total of 2,025 delegates are necessary to secure the Democratic Party's presidential nomination.

Estimates can vary because of the complicated formula of allocating Democratic delegates that considers the candidate's statewide performance in a given primary or caucus, as well as the candidate's performance in each of that state's individual congressional districts. Reporting complete vote totals from numerous districts can take time.

On the Republican side, it takes 1,191 delegates to win the nomination. Based on frontrunner John McCain's strong showing in the Super Tuesday primaries and caucuses, most news organizations project McCain is at least halfway toward his goal of winning the nomination.